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Thermophoresis, or thermodiffusion, is becoming a more popular method for investigating the interactions between proteins and ligands due to its high sensitivity to the interactions between solutes and water. Despite its growing use, the intricate mechanisms behind thermodiffusion remain unclear. This gap in knowledge stems from the complexities of thermodiffusion in solvents that have specific interactions as well as the intricate nature of systems that include many components with both non-ionic and ionic groups. To deepen our understanding, we reduce complexity by conducting systematic studies on aqueous salt solutions. In this work, we focused on how guanidinium salt solutions behave in a temperature gradient, using thermal diffusion forced Rayleigh scattering experiments at temperatures ranging from 15 to 35 °C. We looked at the thermodiffusive behavior of four guanidinium salts (thiocyanate, iodide, chloride, and carbonate) in solutions with concentrations ranging from 1 to 3 mol/kg. The guanidinium cation is disk-shaped and is characterized by flat hydrophobic surfaces and three amine groups, which enable directional hydrogen bonding along the edges. We compare our results to the behavior of salts with spherical cations, such as sodium, potassium, and lithium. Our discussions are framed around how different salts are solvated, specifically in the context of the Hofmeister series, which ranks ions based on their effects on the solvation of proteins. [ABSTRACT FROM AUTHOR]

We developed a spectroscopic method for directly obtaining the spectra of electromagnetic (EM) enhancement of plasmonic hotspots (HSs). The method was applied to one-dimensional (1D) HSs generated between silver nanowire (NW) dimers. The EM enhancement spectra were derived by dividing the spectra of surface-enhanced fluorescence (SEF) from single NW dimers with SEF obtained from large nanoparticle aggregates, where aggregate-by-aggregate variations in the SEF spectra were averaged out. Some NW dimers were found to exhibit EM enhancement spectra that deviated from the plasmon resonance Rayleigh scattering spectra, indicating that their EM enhancement was not generated by superradiant plasmons. These experimental results were examined by numerical calculation based on the EM mechanism by varying the morphology of NW dimers. The calculations reproduced the spectral deviations as the NW diameter dependence of EM enhancement. Phase analysis of the enhanced EM near-fields along the 1D HSs revealed that the dipole–quadrupole coupled plasmon, which is a subradiant mode, mainly generates EM enhancement for dimers with NW diameters larger than ∼80 nm, which was consistent with scanning electron microscopic measurements. [ABSTRACT FROM AUTHOR]

A novel gold nanocluster surface molecularly imprinted polyisopropylacrylamide probe (AuNC@MIP) was synthesized for the specific detection of NO2−, using N-isopropylacrylamide (NIPAM) as the functional monomer, gold nanoclusters (AuNC) as the substrate, ethylene glycol dimethacrylate (EGDMA) as the cross-linking agent, and nitrosophenol (NPN) produced from sodium nitrite (NaNO2) and phenol (PN) as the template molecule, N,N-dimethylformamide (DMF) as the solvent, and azobisisobutyronitrile (AIBN) as the initiator. The nanoprobe was characterized using molecular spectroscopy, XPS, TEM, TGA, and zeta potential analysis. The probes revealed a prominent resonance Rayleigh scattering (RRS) peak at 370 nm. Upon addition of NO2−, the RRS intensity at 370 nm decreased due to the RRS energy transfer enhancing. The linear determination range is 0.125–1.50 nmol/L NO2−, with a limit of detection (LOD) of 0.085 nmol/L. The new RRS method was applied to determine NO2− in meat, dairy products, and water samples, with recovery of 96–107% also relative standard deviations (RSDs) of 1.1–8.0%. [ABSTRACT FROM AUTHOR]

Landmines pose significant humanitarian and strategic challenges, threatening both civilian populations and military operations worldwide. This study presents a practical simulation method based on Rayleigh and Compton scattering ratios to determine the effective atomic number of low atomic number (low-Z) explosives used in landmines. Utilizing the Monte Carlo N-Particle (MCNP) simulation program, Rayleigh/Compton scattering ratios were obtained using a Ge(Li) detector at a scattering angle of 115° within a simulated geometry. The simulation results were found to be in good agreement with experimental data, confirming the reliability of the method. Pure elements with atomic numbers ranging from 3 to 20 and various explosives were irradiated with photons of 59.54 keV energy to obtain scattering spectra. The effective atomic numbers calculated using Rayleigh/Compton scattering ratios were compared with five different theoretical methods, yielding consistent results. These findings demonstrate that the proposed method can reliably determine the effective atomic number of low-Z elements and explosives containing these elements. Additionally, the study confirms that MCNP simulations can be effectively utilized in various fields such as defense industry, radiation safety, medical applications, and radiation dosimetry.HIGHLIGHTS The effective atomic numbers of explosives in nine different landmines were determined using the MCNP simulation and compared with conventional methods.The MCNP simulation method offers a more practical and reliable approach for determining the effective atomic numbers of explosives.The Rayleigh-to-Compton scattering ratio was shown to accurately determine the effective atomic numbers of low atomic number materials.This method has significant potential for application in the detection of landmine explosives, providing a more effective alternative to conventional approaches.The effective atomic numbers of explosives in nine different landmines were determined using the MCNP simulation and compared with conventional methods.The MCNP simulation method offers a more practical and reliable approach for determining the effective atomic numbers of explosives.The Rayleigh-to-Compton scattering ratio was shown to accurately determine the effective atomic numbers of low atomic number materials.This method has significant potential for application in the detection of landmine explosives, providing a more effective alternative to conventional approaches. [ABSTRACT FROM AUTHOR]

The present work deals with the linear and nonlinear optical properties (the dipole moment, polarizability, total hyperpolarizability, electric field–induced second harmonic generation, and hyper-Rayleigh scattering first hyperpolarizability) of five C-acylated pyrazoles as essential compounds with specific photophysical properties. Based on density functional theory at different functionals (B3LYP, PBE0, BVP86, CAM-B3LYP, and ωB97X-D), the properties have been successfully calculated and analysed extensively to limelight on the nonlinear optical activity. The obtained results show a high total first hyperpolarizability β tot up to 1240 a.u. and low energy gap E g less than 2.7 eV. An inverse relationship has been obtained between the β tot and E g . The calculated E g values confirm that charge occurs within the C-acylated pyrazoles. This study may provide new ways to utilize these analogues as NLO materials. [ABSTRACT FROM AUTHOR]

Advancements in Raman light sheet microscopy have provided a powerful, non-invasive, marker-free method for imaging complex 3D biological structures, such as cell cultures and spheroids. By combining 3D tomograms made by Rayleigh scattering, Raman scattering, and fluorescence detection, this modality captures complementary spatial and molecular data, critical for biomedical research, histology, and drug discovery. Despite its capabilities, Raman light sheet microscopy faces inherent limitations, including low signal intensity, high noise levels, and restricted spatial resolution, which impede the visualization of fine subcellular structures. Traditional enhancement techniques like Fourier transform filtering and spectral unmixing require extensive preprocessing and often introduce artifacts. More recently, deep learning techniques, which have shown great promise in enhancing image quality, face their own limitations. Specifically, conventional deep learning models require large quantities of high-quality, manually labeled training data for effective denoising and super-resolution tasks, which is challenging to obtain in multi-modal microscopy. In this study, we address these limitations by exploring advanced zero-shot and self-supervised learning approaches, such as ZS-DeconvNet, Noise2Noise, Noise2Void, Deep Image Prior (DIP), and Self2Self, which enhance image quality without the need for labeled and large datasets. This study offers a comparative evaluation of zero-shot and self-supervised learning methods, evaluating their effectiveness in denoising, resolution enhancement, and preserving biological structures in multi-modal Raman light sheet microscopic images. Our results demonstrate significant improvements in image clarity, offering a reliable solution for visualizing complex biological systems. These methods establish the way for future advancements in high-resolution imaging, with broad potential for enhancing biomedical research and discovery. [ABSTRACT FROM AUTHOR]

Ultrasonic biochemical detection is important for biomarker detection, drug monitoring, and medical diagnosis, as it can predict disease progression and enable effective measures to be taken in a timely manner. However, the ultrasonic technology currently used for biochemical marker detection is directly modified on the surface of the device. The associated test methods are costly and unreliable while having poor repeatability; therefore, they cannot achieve low-cost rapid testing. In this study, a detection mechanism based on the Rayleigh scattering of acoustic waves caused by nanoparticles, which causes changes in the received sound pressure, was developed for the first time. The modification of antibodies on an insertable substrate decouples the functionalization step from the sensor surface and facilitates the application of capacitive micromachined ultrasonic transducers (CMUTs) in conjunction with Au nanoparticles (AuNPs) for CA19-9 cancer antigen detection. A corresponding detection theory was established, and the relevant parameters of the theoretical formula were verified using different nanoparticles. Using our fabricated CMUT chip with a resonant frequency of 1 MHz, the concentrations and substances of the CA19-9 antigen markers were successfully measured. In the concentration range of 0.1–1000 U/mL, the receiving voltage decreased with increasing concentration. Further investigations revealed that the influence of other interfering markers in the human body can be ignored, demonstrating the feasibility and robustness of biochemical detection based on CMUTs combined with nanoparticles. [ABSTRACT FROM AUTHOR]

A multi-wavelength actively Q-switched random fiber laser based on real-time configurable Waveshaper and electro-optic modulator is proposed and experimentally demonstrated. The random feedback of the laser is provided by Rayleigh scattering generated by the single-mode fiber. The Waveshaper not only acts as a multi-channel filter, but also introduces wavelength-dependent losses in the laser cavity, which can suppress the mode competition caused by uniform broadening of the erbium-doped fiber and the power imbalance caused by Rayleigh scattering. Additional dispersion, group delay, phase and other parameters can be introduced through Waveshaper, and then the influence of additional quantities such as dispersion on actively Q-switched random fiber laser is studied. In the experiment, when the additional dispersion changes within -200 ~ 200 ps/nm, the pulse width of actively Q-switched can change between 1.01 ~ 1.18 μs. Compared with other experiments, this experiment further and more accurately studied the effects of dispersion, group delay and phase on actively Q-switched pulses. Because of the half-open cavity and erbium-doped fiber gain, the laser threshold is suppressed to 25 mW. The powers distribution on the wavelengths are uniform, and the amplitude difference between the ten wavelengths is < 2 dB. The side-mode suppression ratio of the laser after equalization is about 25 dB. When a triangle waveform is applied to the EOM, a dark pulse sequence output can be obtained. The proposed multi-wavelength actively Q-switched random fiber laser has the advantages of simple structure, low threshold and high stability. [ABSTRACT FROM AUTHOR]

Light is a fundamental attribute and key abiotic driver in forest ecosystems. Although the ecological effects of light itself is well studied, capturing the complex parameters that constitute the whole light environment remain an intricate research endeavor. Here, we apply the newly introduced environmental light field (ELF) technique in Kibale National Park, Uganda. We captured whole light scenes with repeat photography and processed it to measure both the spectral composition of light in the red‐green‐blue range, as well as its variation, or "contrast‐span", using the newly introduced International System of Units (SI); "lit". We compare across major and globally common utilized forest types—primary, secondary, and selectively logged areas, as well as a completely cleared area as a control. We find that the ELF system is able to effectively capture key aspects of the local light environment across the range of forest types. The distribution of light intensity and its spectral composition across our study is hardly uniform, with primary forest and a clearing showing two orders of magnitude difference in light. Blue light predominates the sky areas of the clearing, indicating the Rayleigh scattering of sunlight in the atmosphere. In general, radiance decrease with increasing intactness of the forest, and selectively logged and primary forest show the most similar environmental light characteristics. Owing to its ability to capture fine scale variations in light across elevation gradients, their spectral characteristics, as well as their intensities, the ELF system should become a useful tool in better quantifying light in ecology. In particular, we discuss its potential use in restoration ecology. [ABSTRACT FROM AUTHOR]

A new processing method is developed to analyze images from a Fabry-Pérot interferometer in order to extract point measurements of temperature and velocity within a gas flow, using Rayleigh scattering. Two types of interferograms are generated from a Fabry-Pérot model combined with a simulated light source. The first type is obtained from a diffuse coherent light source, namely, a laser beam on a diffuser. The interferometer characteristics, defined by only two independent parameters, are retrieved within 0.1% accuracy. The knowledge of these parameters is mandatory to analyze interferograms from Rayleigh scattered light. The second type corresponds to Rayleigh scattered light from a small volume under flow conditions, lighted with a focused laser beam and captured with long exposure time. Several flow parameters are chosen to generate these interferograms. The relative errors on the temperature and velocity estimates are found to be weak. Noise is also added to assess the robustness of the processing method. The error induced by the estimates of the instrument function is found to be of second order compared to the error induced by the image analysis. [ABSTRACT FROM AUTHOR]

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This study evaluated the potential of the Single Scattering Radiative Transfer (SSRT) model coupled with the Oh model to retrieve surface soil moisture (SSM) in two drip-irrigated wheat fields in the Tensift al Haouz plain, over three growing seasons (2016–2019). This research focuses on evaluating isotropic scattering and Rayleigh scattering by calibrating the coupled SSRT_Oh model, using data gathered on the calibrated field. The data includes measured SSM at 5 cm depth, Leaf Area Index (LAI) and vegetation height (H). The aim is to fit the extinction coefficient through comparing simulated and Sentinel-1 backscatter, at VV and VH polarizations. The validated field data were used to retrieve SSM. Calibration revealed the best retrieval for Rayleigh scattering, at VV polarization, with an RMSE of 1.25 dB, a correlation coefficient (r) of 0.86, and a bias of 0.1 dB, whereas, the isotropic approach yielded r, RMSE and bias values of 0.83, 1.37 dB and −0.01 dB, respectively. Rayleigh's performance remained unchanged throughout the inversion process for SSM retrieval, at VV polarization, with r of 0.87 against 0.86 for isotropic scattering. To enhance our findings, the introduction of dynamic extinction parameter and exclusive use of Sentinel-1 data to describe vegetation could improve SSM retrieval. [ABSTRACT FROM AUTHOR]

This paper investigates how atmospheric vertical profiles of pressure, temperature, and concentration affect molecular absorption calculation. This sensitivity analysis is performed in preparation to the upcoming TRUTHS mission, anticipated to provide hyperspectral TOA BRF records with a radiometric accuracy better than 1%. Two methods for characterizing the atmospheric vertical profile are compared: rescaling the H2O and O3 concentrations of an AFGL U.S. Standard vertical profile, and using customized profiles based on CAMS data. The study investigates the effects of those methods on multi-spectral observations in key spectral regions affected, respectively, by water vapour, ozone and methane, as well as on hyperspectral observations covering the visible to SWIR region. Results show that when molecular transmittance exceeds 97%, the choice of method has minimal impact, with less than 1% uncertainty. When the molecular transmittance decreases from 97% to 75%, the corresponding uncertainty on the TOA BRF simulation increases from 1% up to 5%. For transmittance below 75%, using CAMS data for vertical profile characterization is recommended. The study also highlights how pressure and temperature profiles influence Rayleigh optical thickness estimation, particularly affecting TOA BRF in the blue spectral region. [ABSTRACT FROM AUTHOR]

Optimizing the use of existing high-voltage transmission lines demands real-time condition monitoring to ensure structural integrity and continuous service. Operating these lines at the current capacity is limited by safety margins based on worst-case weather scenarios, as exceeding these margins risks bringing conductors dangerously close to the ground. The integration of optical fibers within modern transmission lines enables the use of Distributed Fiber Optic Sensing (DFOS) technology, with Chirped-Pulse Phase-Sensitive Optical Time-Domain Reflectometry (CP- Φ OTDR) proving especially effective for this purpose. CP- Φ OTDR measures wind-induced vibrations along the conductor, allowing for an analysis of frequency-domain vibration modes that correlate with conductor length and sag across spans. This monitoring system, capable of covering distances up to 40 km from a single endpoint, enables dynamic capacity adjustments for optimized line efficiency. Beyond sag monitoring, CP- Φ OTDR provides robust detection of external threats, including environmental interference and mechanical intrusions, which could compromise cable stability. By simultaneously monitoring the Optical Phase Conductor (OPPC) and Optical Ground Wire (OPGW), this study offers the first comprehensive, real-time evaluation of both structural integrity and potential external aggressions on overhead transmission lines. The findings demonstrate that high-frequency data offer valuable insights for classifying mechanical intrusions and environmental interferences based on spectral content, while low-frequency data reveal the diurnal temperature-induced sag evolution, with distinct amplitude responses for each cable. These results affirm CP- Φ OTDR's unique capacity to enhance line safety, operational efficiency, and proactive maintenance by delivering precise, real-time assessments of both structural integrity and external threats. [ABSTRACT FROM AUTHOR]

In this paper, a time-domain solution for Rayleigh wave scattering from a complex site of Alpine Valley is presented based on the scaled boundary finite element method (SBFEM). Both the near-field region and the far-field region are assumed to be homogeneous, isotropic linear elastomers, where the near-field region is discretized using the quadtree method and the far-field region is simulated with a displacement unit impulse response function. The input of Rayleigh waves is solved by the equivalent loading method. The scattering behavior of seismic waves in alpine valleys is comprehensively analyzed, and the results are of theoretical significance for site safety evaluation and seismic defenses. [ABSTRACT FROM AUTHOR]

In this work, nanostructured and transparent cellulose aerogels are synthesized via a purely salt induced approach from non‐modified microcrystalline cellulose type II. The production process requires in contrast to state of the art methods no pretreatment of cellulose or use of expensive cellulose‐solvents: it consists of hydrogel formation via cross‐linking of cellulose with calcium ions, a solvent exchange and a supercritical drying step. A systematic multiparameter study reveals that a high level of structural control is achievable: ratios of macro‐ to mesoporosity and the size of mesopores can be tailored by adjustment of the calcium ion content, while keeping a high overall porosity in the range of 92% – 96 %. The build‐up of homogeneous, fine pore structures results in a significant increase of the specific surface area as compared to conventional calcium‐free aerogels (684 vs. 300 m2 g−1). Remarkably, the Ca2+‐cross‐linking renders aerogels transparent, with Rayleigh scattering being the dominant scattering mechanism. Additional ion exchange to Ca2+ in the hydrogel‐state leads to further reduction of the pore size and to products with optimized optical properties, e.g., light transmission of 91% at an incidents light wavelength of 800 nm and a substrate thickness of 1.5 mm. [ABSTRACT FROM AUTHOR]

This study presents an advanced integration of Multi-modal Raman Light Sheet Microscopy with zero-shot learning-based computational methods to significantly enhance the resolution and analysis of complex three-dimensional biological structures, such as 3D cell cultures and spheroids. The Multi-modal Raman Light Sheet Microscopy system incorporates Rayleigh scattering, Raman scattering, and fluorescence detection, enabling comprehensive, marker-free imaging of cellular architecture. These diverse modalities offer detailed spatial and molecular insights into cellular organization and interactions, critical for applications in biomedical research, drug discovery, and histological studies. To improve image quality without altering or introducing new biological information, we apply Zero-Shot Deconvolution Networks (ZS-DeconvNet), a deep-learning-based method that enhances resolution in an unsupervised manner. ZS-DeconvNet significantly refines image clarity and sharpness across multiple microscopy modalities without requiring large, labeled datasets, or introducing artifacts. By combining the strengths of multi-modal light sheet microscopy and ZS-DeconvNet, we achieve improved visualization of subcellular structures, offering clearer and more detailed representations of existing data. This approach holds significant potential for advancing high-resolution imaging in biomedical research and other related fields. [ABSTRACT FROM AUTHOR]

The role of various light scattering phenomena in aesthetics and clinical practice is explored in this review. Four main types of light scattering, Tyndall, Rayleigh, Mie, and Raman, are discussed. Each type is explained in terms of its physical principles and its applications in aesthetic medicine. Tyndall scattering is relevant in understanding the blue appearance of certain dermal fillers. Rayleigh scattering contributes to skin tone perception and plays a role in certain laser treatments. Mie scattering is important in laser hair removal and the appearance of skin conditions like melasma. Raman scattering, while primarily used in research, shows promise for non‐invasive skin analysis, personalized skincare, treatment monitoring, and early skin cancer detection. It is important to understand these scattering phenomena for optimizing light‐based aesthetic procedures and developing effective treatments. Properly applying the appropriate scattering theory based on relative particle size is crucial in clinical aesthetic practice. [ABSTRACT FROM AUTHOR]

The recent developments in array-based surface-wave tomography have made it possible to directly measure apparent phase velocities through wave front tracking. While directionally dependent measurements have been used to infer intrinsic |$2\psi $| azimuthal anisotropy (with a 180° periodicity), a few studies have also demonstrated strong but spurious |$1\psi $| azimuthal anisotropy (360° periodicity) near major structure boundaries particularly for long period surface waves. In such observations, Rayleigh waves propagating in the direction perpendicular to the boundary from the slow to the fast side persistently show a higher apparent velocity compared to waves propagating in the opposite direction. In this study, we conduct numerical and theoretical investigations to explore the effect of scattering on the apparent Rayleigh-wave phase velocity measurement. Using 2-D spectral-element numerical wavefield simulations, we first reproduce the observation that waves propagating in opposite directions show different apparent phase velocities when passing through a major velocity contrast. Based on mode coupling theory and the locked mode approximation, we then investigate the effect of the scattered fundamental-mode Rayleigh wave and body waves interfering with the incident Rayleigh wave separately. We show that scattered fundamental-mode Rayleigh waves, while dominating the scattered wavefield, mostly cause short wavelength apparent phase velocity variations that could only be studied if the station spacing is less than about one tenth of the surface wave wavelength. Scattered body waves, on the other hand, cause longer wavelength velocity variations that correspond to the existing real data observations. Because of the sensitivity of the |$1\psi $| apparent anisotropy to velocity contrasts, incorporating such measurements in surface wave tomography could improve the resolution and sharpen the structural boundaries of the inverted model. [ABSTRACT FROM AUTHOR]

CaBi2Nb2O9 (CBN) ceramic is a promising sensing element to convert vibration to electrical signal at temperatures higher than 600°C. However, conventionally sintered ceramics suffer from poor piezoelectric coefficient (d33) and low electrical resistivity (ρdc). Here, we report that CBN ceramics can be prepared by microwave sintering (MS) to mitigate volatilization issue of Bi2O3 and thus suppress the generation of oxygen vacancies usually seen in conventional sintering (CS) as demonstrated by X‐ray photoelectron spectroscopy (XPS) analysis and mass‐loss measurement. As compared to the CS, the MS is more favorable for reducing the sintering time, and obtaining a dense, fine, and uniform grain morphology as revealed by scanning electron microscopy (SEM) characterizations of both surface and interior of the CBN ceramics, leading to an enhancement of 86% and 75% in d33 and ρdc, respectively. Piezoresponse force microscopy (PFM) as combined with Rayleigh law analysis clearly revealed that the enhancement of piezoelectric properties was attributed to the thinner domains, the higher domain wall density, and the enhanced domain wall motion in the MS‐940 samples. This study paves an important road to simultaneously improve both d33 and ρdc in CBN ceramics for developing high‐temperature vibration sensors. [ABSTRACT FROM AUTHOR]

A bluish green chalcedony (a micro to crypto polycrystalline form of silica) from Africa has been marketed with the trademark AQUAPRASETM. A multimethodological approach, combining gemological analyses, thin section examination, scanning electron microscopy, X-ray powder diffraction, Raman spectroscopy, and trace elements chemical analyses by LA–ICP–MS, was carried out to characterize this material from a gemological and mineralogical point of view. The chalcedony samples consist of a mixture of quartz and moganite, as shown by the X-ray powder diffraction analysis and Raman spectroscopy. "Aquaprase" showed a strong microstructural zoning in terms of grain size, from macrocrystalline to micro and crypto, and morphology. Trace element variations correlated well with the different colored areas of the samples. In particular, the main chromophore ion present in the bluish green areas of the "aquaprase" chalcedony was chromium, followed by iron and nickel, so this chalcedony could be included in the group of chromium-bearing chalcedony. Rayleigh light scattering contributed to the blue hue of the gems. [ABSTRACT FROM AUTHOR]

Sunlight becomes partially polarized due to Rayleigh scattering while passing through the atmosphere. Many insects such as ants and beetles utilize the polarization information of skylight for navigation. Unlike magnetic compass and GPS, this scheme is free from interference and unlike inertial schemes, its error does not accumulate with time. In recent years this navigation scheme has received a lot of attention for navigation of aerial and terrestrial vehicles. Development of a polarization compass that can provide accurate heading information in different weather conditions will benefit a wide range of applications. Here we report the application of linear regression for implementation of a polarization compass. The model is trained with real sky images and then used to predict the solar azimuth in both clear and cloudy sky conditions. The root mean square errors for both conditions were less than 1°. We also compared the performance of the proposed scheme with that of Hough transform and support vector machine, which have been successfully utilized for the same application in the past. Linear regression outperformed Hough transform for all sky conditions considered, and its performance was comparable with support vector machine. However, unlike the other two methods considered, the accuracy of linear regression will increase significantly when trained with a large set of sky images. Therefore, with sufficient training, linear regression can be a promising option for implementation of polarization compass.

【Objective】In the modern field of communications, optical fibers have become an important transmission medium in optical network systems due to their ultra-high transmission bandwidth and excellent optical properties. Multi-core optical fibers integrate multiple cores within a single fiber cladding to significantly enhance the data transmission capacity of a single fiber. However, an increase in the number of cores can also lead to additional channel impairment effects, which in turn affect the transmission performance and communication quality of the fiber link. Therefore, studying the theoretical model of the channel effects in coupled-core optical fibers, especially clarifying the relationship between the optical time-domain reflectometry process and channel response, can provide important references for the practical deployment and application of multi-core fibers.【Methods】To refine the model of optical time-domain reflection effects in coupled-core optical fibers, the article begins with basic principles, outlining the theories of forward transmission and backward Rayleigh scattering in coupled-core optical fibers. It details the derivation of coupled mode equations and the general expression for Rayleigh scattering power, including definitions and calculation methods for various coefficients such as the total capture factor. Based on the theoretical research, the article also proposes a modeling scheme for Rayleigh scattering effects in coupled-core optical fibers, taking into account the impact of fiber end-face reflection on the transmission process and providing a technical route to verify the Rayleigh scattering effects. Finally, the article processes the transmission data simulated by the model and conducts a comparative analysis based on the set parameters.【Results】The article constructs a simulation model for Rayleigh scattering effects, calculating the scattering power curve received after optical time-domain reflection. The simulation results show that the received scattering power is consistent with the set parameters, with an error within 5%.【Conclusion】The high precision of the results indicates that the model proposed in the article effectively reflects the Rayleigh scattering effects in coupled-core optical fibers, laying a theoretical foundation for accurately testing parameters of coupled-core optical fibers using optical time-domain reflectometry technology.

Mars is the terrestrial planet in the solar system that is closest to the Earth. Studying the atmospheric parameters of Mars and studying the evolutionary history of the Martian environment on this basis is helpful for people to discover signs of extraterrestrial life and to study the trend of climate change on Earth. Mie–Rayleigh scattering lidar is an important technology for detecting parameters from the surface to the middle and upper atmosphere. Because of the different aerosol distributions, Mie scattering and Rayleigh scattering have their own optimal detection ranges. Given the long period and high cost of any deep space exploration program, it is important to conduct sufficient feasibility studies and parameter simulations before the payload is launched. In this study, a parameterized lidar mathematical model and Earth’s atmospheric mode are used to compare with the measured signals of ground-based Mie–Rayleigh scattering lidar, and the correctness of the lidar mathematical model is verified. Using the model, we select the landing area of Tianwen-1 and substitute it into the Martian atmospheric mode, and then the Mie–Rayleigh lidar backscattering signal and the key parameters of the lidar system are systematically analyzed under the conditions of a clean Martian atmosphere and a global sandstorm. In addition, the optimal detection altitude ranges of Mie scattering and Rayleigh scattering on Mars under different atmospheric conditions are obtained, which provides a reference for the practical design and development of the subsequent lidar system for the Martian atmospheric environment.

Recent measurements of the third harmonic scattering responses of molecules have given a new impetus for computing molecular second hyperpolarizabilities (γ) and for deducing structure–property relationships. This paper has employed a variety of wavefunction and density functional theory methods to evaluate the second hyperpolarizability of the p-nitroaniline prototypical push-pull π-conjugated molecule, addressing also numerical aspects, such as the selection of an integration grid and the impact of the order of differentiation vs the achievable accuracy by using the Romberg quadrature. The reliability of the different methods has been assessed by comparison to reference Coupled-Cluster Singles and Doubles with perturbative treatment of the Triples results. On the one hand, among wavefunction methods, the MP2 scheme offers the best accuracy/cost ratio for computing the static γ. On the other hand, using density functional theory, γ remains a challenging property to compute because all conventional, global hybrid or range-separated hybrid, exchange–correlation functionals underestimate static γ values by at least 15%. Even tuning the range-separating parameter to minimize the delocalization errors does not enable to improve the γ values. Nevertheless, the original double-hybrid B2-PLYP functional, which benefits from 27% of PT2 correlation and 53% Hartree–Fock exchange, provides accurate estimates of static γ values. Unfortunately, the best performing exchange–correlation functionals for γ are not necessarily reliable for the first hyperpolarizability, β, and vice versa. In fact, the β of p-nitroaniline (pNA) could be predicted, with a good accuracy, with several hybrid exchange–correlation functionals (including by tuning the range-separating parameter), but these systematically underestimate γ. As for γ, the MP2 wavefunction method remains the best compromise to evaluate the first hyperpolarizability of pNA at low computational cost. [ABSTRACT FROM AUTHOR]

Nucleotides are organic compounds consisting of a phosphate group, a nitrogenous base, namely adenine (A), thymine (T), cytosine (C), or guanine (G), and a sugar, here deoxyribose. The magnitude of the first hyperpolarizability β of these four DNA nucleotides was determined in aqueous solution with the nonlinear optical technique of hyper rayleigh scattering under non resonant conditions at a fundamental wavelength of 800 nm. The smallest value is found to be 1.67 ± 0.15 × 10−30 esu for thymidine-5′-monophosphate and the highest is 1.76 ± 0.16 × 10−30 esu for 2′-guanosine-5′-monophosphate. Polarization resolved studies were also performed to question the symmetry of the first hyperpolarizability tensor and access the ratio of some elements of the first hyperpolarizability tensor. These experimental results were then compared to the theoretical values of these first hyperpolarizabilities obtained with the density functional theory at the level of the PCM-B3LYP/6-31G+(d) basis and taking into account the solvent. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new di-functional nanosurface MICOF catalytic probe was synthesized. • The probe not only recognizes ENR but also strongly catalyzes the Cu 2 O indicator reaction. • A universal MICOF analytical platform was fabricated with the RRS technique. • The platform for determination of ENR in water is simplicity, sensitivity and selectivity. A new nanopalladium surface molecularly imprinted covalent organic framework (MICOF) catalytic probe (Pd@TpPa) for enrofloxacin (ENR) was synthesized by molecular imprinting technology, using 1,3,5-triformylphloroglucinol (Tp) and p-phenylenediamine (Pa) as monomers, ENR as the template molecule, and palladium nanoparticles (PdNP) as the core of nanocatalytic probe. This nanoprobe not only specifically recognizes ENR but also catalyzes the cupric tartrate-glucose (GL) indicator reaction. The amino groups in TpPa replace the tartrate ions, forming a new complex with Cu2+. This new complex enhances the efficiency of GL oxidation reaction. The generated Cu 2 O nanoparticles exhibit strong resonance Rayleigh scattering (RRS) and absorption (Abs) peaks at 370 nm and 500 nm, respectively. The catalytic and analytical performances of metal nanoparticles including Pd, Pt, Au and Ag were studied. It was found that Pd@TpPa ENR exhibited the best performance. The RRS response was linear to ENR concentration in the range of 0.01–1.5 nM, with a detection limit of 0.008 nM ENR. The method was applied to analyze river water samples, yielding recoveries of 96.9–106.6 % and precision between 2.33–8.49 %. This nanocatalytic probe-RRS analysis platform is simple, sensitive, selective, and versatile, making it applicable for the determination of norfloxacin (NOR), ofloxacin, pefloxacin, fleroxacin, and ciprofloxacin, with linear ranges of 0.02–6.0 nM, 0.04–6.0 nM, 0.04–6.0 nM, 0.1–15 nM, and 0.1–15 nM, respectively. [ABSTRACT FROM AUTHOR]

The relationship between the electromagnetic (EM) enhancement of the optical responses of molecules and plasmon resonance has been investigated using Rayleigh scattering or the extinction spectra of plasmonic systems coupled with molecular excitons. However, quantum optics predicts that the EM enhancement of such optical responses, e.g., fluorescence, Raman, and their nonlinear counterparts, is related directly to optical absorption and indirectly to Rayleigh scattering and extinction. To demonstrate this prediction, a micro-spectroscopic method for obtaining Rayleigh scattering, extinction, absorption, and EM enhancement is developed using single-coupled plasmonic systems composed of silver nanoparticle dimers and dye molecules. The EM enhancement is derived from ultrafast surface-enhanced fluorescence. An evaluation of the spectral relationships demonstrates that the EM enhancement can be reproduced better by absorption than by Rayleigh scattering or extinction. This reproduction is phenomenologically confirmed by numerical calculations based on classical electromagnetism, indicating the importance of absorption spectroscopy in coupled plasmonic systems for evaluating EM enhancement. [ABSTRACT FROM AUTHOR]

In this study, the properties of Rayleigh wave fields scattered at a surface from open vertical cracks with different shapes are investigated. The scattered Rayleigh wave is determined by both the incident Rayleigh wave and its interaction with the crack, and the wave fields are modeled using the Green's function method based on the reciprocity theorem. The reflection coefficient of the Rayleigh wave in two-dimensional coordinates is employed to simplify the area integration over the crack surface for the scattered Rayleigh wave to a line integration over the length of the crack. Numerical simulations are carried out, and the effects of the crack length and depth on the scattered Rayleigh wave fields are discussed. The results indicate that the distribution of a scattered Rayleigh wave field is mainly determined by the crack length, while the amplitude is closely related to the crack depth. Since the reflection coefficient becomes almost stable when the ratio of the crack depth to the Rayleigh wavelength is larger than 1, the variation in the scattered Rayleigh wave field is insignificant for cracks with the same length but varying depths. This work will be helpful for solving the inverse problem of evaluating crack geometry using ultrasonic Rayleigh waves and for further work on Rayleigh waves scattered by cracks with different directions of extension and angles with the surface. [ABSTRACT FROM AUTHOR]

This work reports on the first computational quantum-chemistry implementation of the hyper-Rayleigh scattering optical activity (HRS-OA), a nonlinear chiroptical phenomenon. First, from the basics of the theory, which is based on quantum electrodynamics, and focusing on the electric dipole, magnetic-dipole, and electric-quadrupole interactions, the equations for the simulation of the differential scattering ratios of HRS-OA are re-derived. Then, for the first time, computations of HRS-OA quantities are presented and analyzed. They have been enacted on a prototypical chiral organic molecule (methyloxirane) at the time-dependent density functional theory level using a broad range of atomic orbital basis sets. In particular, (i) we analyze the basis set convergence, demonstrating that converged results require basis sets with both diffuse and polarization functions, (ii) we discuss the relative amplitudes of the five contributions to the differential scattering ratios, and (iii) we study the effects of origin-dependence and derived the expression of the tensor shifts and we prove the origin-independence of the theory for exact wavefunctions. Our computations show the ability of HRS-OA as a nonlinear chiroptical method, able to distinguish between the enantiomers of the same chiral molecule. [ABSTRACT FROM AUTHOR]

Molecular scattering (Rayleigh scattering) has been extensively used from the ground with lidars and from space to observe the limb, thereby deriving vertical temperature profiles between 30 and 80 km. In this study, we investigate how temperature can be measured using the new Ozone Mapping and Profiler Suite (OMPS) sensor, aboard the Suomi NPP and NOAA-21 satellites. The OMPS consists of three instruments whose main purpose is to study the composition of the stratosphere. One of these, the Limb Profiler (LP), measures the radiance of the limb of the middle atmosphere (stratosphere and mesosphere, 12 to 90 km altitude) at wavelengths from 290 to 1020 nm. This new data set has been used with a New Simplified Radiative Transfer Model (NSRTM) to derive temperature profiles with a vertical resolution of 1 km. To validate the method, the OMPS-derived temperature profiles were compared with data from four ground-based lidars and the ERA5 and MSIS models. The results show that OMPS and the lidars are in agreement within a range of about 5 K from 30 to 80 km. Comparisons with the models also show similar results, except for ERA5 beyond 50 km. We investigated various sources of bias, such as different attenuation sources, which can produce errors of up to 120 K in the UV range, instrumental errors around 0.8 K and noise problems of up to 150 K in the visible range for OMPS. This study also highlighted the interest in developing a new miniaturised instrument that could provide real-time observation of atmospheric vertical temperature profiles using a constellation of CubeSats with our NSRTM. [ABSTRACT FROM AUTHOR]

In Brillouin optical correlation-domain reflectometry (BOCDR), sinusoidal modulation is applied to the output frequency of a light source, with spatial resolution inversely related to the modulation amplitude. We have developed an effective method to estimate the modulation amplitude using the width of the noise spectrum caused by Rayleigh scattering, eliminating the need for an optical spectrum analyzer or modifications to existing equipment. However, the Rayleigh noise spectrum often displays a three-layered structure, complicating the identification of the appropriate spectral components for estimating the modulation amplitude. In this work, we investigate the origins of this three-layered Rayleigh noise spectrum and identify the directivity of an optical circulator as the source of the third noise component. As replacing the circulator with alternative optical components is not easy, it remains an essential part of the system. Our analysis shows that the third noise component exhibits significantly small variation in spectral width with changes in modulation frequency compared to the first and second components. This characteristic allows for the effective separation and identification of the third noise component, thereby enhancing the accuracy and convenience of modulation amplitude estimation in BOCDR. [ABSTRACT FROM AUTHOR]

Experiments of shock wave/boundary layer interactions over a nominally two-dimensional compression ramp are conducted in a Mach 4 Ludwieg tube tunnel. Measurements of Schlieren, Rayleigh scattering, and surface pressure are performed to present the relevant flow features. The effects of two parameters, namely the Reynolds number based on the length of the flat plate and the ramp angle, on the flow stabilities are focused on. Four ramp angles of 6°, 8°, 10°, and 12° are tested under a Reynolds number of 7.22 × 105, while two other Reynolds numbers (3.66 × 105 and 9.19 × 105) are investigated with a ramp angle of 10°. Streamwise streaks are observed downstream of the reattachment point. The spanwise wavelength of the streaks remains unchanged with different ramp angles, whereas it slightly decreases as the Reynolds number increases. Power spectral density results show that the flow is transitional in the streak region and becomes turbulent where streaks break down. When increasing the ramp angle or the Reynolds number, the streamwise length of streaks shrinks. Two different patterns are distinguished at the breakdown, resembling the two unstable modes observed in the breakdown of Görtler vortices. To clarify the underlying physics of the formation of streaks, global stability analysis and resolvent analysis are carried out. Two regions of maximum optimal gain are identified, which are associated with Mack's first mode and streaks. The former can serve as an initial seed of Görtler instability via nonlinear interaction, while the latter can be associated with transient growth due to the lift-up mechanism and Görtler instability. [ABSTRACT FROM AUTHOR]

In this article, the propagation and scattering of Rayleigh wave from an interfacial crack in a bilayer structure, a viscoelastic waveguide layer attached to a piezoelectric substrate, have been examined. The Principle of Superposition is used to formulate the problem. The Fourier transform method and stiffness matrix formulation have been used to arrive at singular integral equations. These singular integral equations are then reduced to a system of linear algebraic equations by applying the Gauss-Jacobi quadrature technique. A parametric study has been examined for phase velocity, attenuation, and dynamic stress intensity factor of mode-I and mode-II at both crack-tip. [ABSTRACT FROM AUTHOR]

Hydrogen-bonded interactions of organic acids play crucial role in many chemical and biochemical processes vital for life's maintenance. They are important as well in the context of secondary aerosol formation in the atmosphere. In the present work, we study the nature of hydrogen-bonded acid–base interactions present in the binary clusters of vanillic acid, a natural phenolic compound found in various plants and also observed in Amazonian aerosol, with common atmospheric bases such as ammonia and methylamines (mono-, di-, and tri-methylamine). Detailed and systematic quantum-chemical DFT calculations have been performed to analyze the structural, energetic, electrical, and spectroscopic properties of the clusters. The presence of strong intermolecular hydrogen-bonds and large binding electronic energies indicates that vanillic acid interacts strongly with atmospheric molecules. Scattering intensities of radiation (Rayleigh activities) are found to increase with cluster formation. The changes in binding free energy and enthalpy of formation of the vanillic acid-ammonia/amine binary clusters at lower temperatures demonstrate increased thermodynamical stability. [ABSTRACT FROM AUTHOR]

In recent years, flexible pressure sensors have garnered significant attention. However, the development of large-area, low-cost, and easily fabricated flexible pressure sensors remains challenging. We designed a flexible fiber optic pressure sensor for contact force detection based on the principle of backward Rayleigh scattering using a single-mode optical fiber as the sensing element and polymer PDMS as the encapsulation material. To enhance the sensor's sensitivity and stability, we optimized its structural design, parameters, and fabrication process and measured the fiber strain using an optical frequency domain reflectometer (OFDR). The results showed that the sensor achieved a high sensitivity of 6.93247 με/kPa with a PDMS concentration ratio of 10:1, a curing time of 2 h, and a substrate thickness of 5 mm. The sensor demonstrated excellent linearity and repeatability in static performance tests and was successfully used to monitor the plantar pressure distribution in real time. This flexible fiber optic pressure sensor can be developed via a simple fabrication process, has a low cost, and has high sensitivity, highlighting its potential applications in smart wearables and medical diagnostics. [ABSTRACT FROM AUTHOR]

Raman fiber lasers (RFLs), which are based on the stimulated Raman scattering effect, generate laser beams and offer distinct advantages such as flexibility in wavelength, low quantum defects, and absence from photo-darkening. However, as the power of the RFLs increases, heat generation emerges as a critical constraint on further power scaling. This escalating thermal load might result in transverse mode instability (TMI), thereby posing a significant challenge to the development of RFLs. In this work, a static model of the TMI effect in a high-power Raman fiber amplifier based on stimulated thermal Rayleigh scattering is established considering higher-order mode excitation. The variations of TMI threshold power with different seed power levels, fundamental mode purities, higher-order mode losses, and fiber lengths are investigated, while a TMI threshold formula with fundamental mode pumping is derived. This work will enrich the theoretical model of TMI and extend its application scope in TMI mitigation strategies, providing guidance for understanding and suppressing TMI in the RFLs. [ABSTRACT FROM AUTHOR]

Spectral analysis of light is one of the oldest and most versatile scientific methods and the basis of countless techniques and instruments. Miniaturized spectrometers have recently seen great advances, but challenges remain before they are widely deployed. We report an integrated photonic spectrometer that achieves high performance with minimal component complexity by combining imaging of light propagation patterns in multi-mode interference waveguides with machine learning analysis. We demonstrate broadband operation in the visible and near-infrared, 0.05 nm spectral resolution, and an array of four spectrometers on a single chip. Two canonical applications are implemented: spectral analysis of the solar spectrum with neural network reconstruction and detection of Rayleigh scattering from microbeads on an optofluidic chip using principal component classification. These results illustrate the potential of this approach for high-performance spectroscopy across disciplines. [ABSTRACT FROM AUTHOR]

This research introduces an innovative application of physics-informed neural networks (PINNs) to tackle the intricate challenges of radiative transfer (RT) modelling in exoplanetary atmospheres, with a special focus on efficiently handling scattering phenomena. Traditional RT models often simplify scattering as absorption, leading to inaccuracies. Our approach utilizes PINNs, noted for their ability to incorporate the governing differential equations of RT directly into their loss function, thus offering a more precise yet potentially fast modelling technique. The core of our method involves the development of a parametrized PINN tailored for a modified RT equation, enhancing its adaptability to various atmospheric scenarios. We focus on RT in transiting exoplanet atmospheres using a simplified 1D isothermal model with pressure-dependent coefficients for absorption and Rayleigh scattering. In scenarios of pure absorption, the PINN demonstrates its effectiveness in predicting transmission spectra for diverse absorption profiles. For Rayleigh scattering, the network successfully computes the RT equation, addressing both direct and diffuse stellar light components. While our preliminary results with simplified models are promising, indicating the potential of PINNs in improving RT calculations, we acknowledge the errors stemming from our approximations as well as the challenges in applying this technique to more complex atmospheric conditions. Specifically, extending our approach to atmospheres with intricate temperature-pressure profiles and varying scattering properties, such as those introduced by clouds and hazes, remains a significant area for future development. [ABSTRACT FROM AUTHOR]

The existing long-distance transmission line perception mainly focuses on the measurement and analysis of electrical parameters. When the line is subject to wind vibration, icing or galloping, the changes of electrical parameters are not obvious and difficult to capture, resulting in poor performance of long-distance transmission line fault state perception. In this regard, the long-distance transmission line condition sensing based on distributed optical fiber sensing technology is studied. This method designs corresponding sensing methods for four working conditions: using the back Brillouin scattering sensor and phase sensitive Rayleigh scattering sensor in the optical fiber sensing technology to form a multi parameter distributed optical fiber sensing device, which is used to sense the surface temperature, vibration, strain and other data of the long-distance transmission line; By analyzing the linear relationship between fiber Brillouin frequency shift and Brillouin power and fiber strain and temperature, the sensing results of icing thickness of long-distance transmission lines are obtained; By calculating the amplitude and phase information of the detection signal, the sensing results of long-distance transmission line vibration are obtained; By calculating the time difference of polarization mutation signal at both ends of long-distance transmission line, combined with the propagation speed of optical signal and the length of long-distance transmission line, the perception result of lightning fault location of long-distance transmission line can be obtained. The experimental results show that this method can more accurately collect the real-time operation data of long-distance transmission lines, and can effectively perceive the galloping, wind vibration and lightning fault location of long-distance transmission lines. [ABSTRACT FROM AUTHOR]

This article presents a comprehensive study on the impact of irradiation optical fiber cores with a femtosecond-pulsed laser, operating at a wavelength of 1030 nm, on the signal amplitude in Rayleigh scattering-based optical frequency domain reflectometry (OFDR). The experimental study involves two fibers with significantly different levels of germanium doping: the standard single-mode fiber (SMF-28) and the ultra-high numerical aperture fiber (UHNA7). The research findings reveal distinct characteristics of reflected and scattered light amplitudes as a function of pulse energy. Although different amplitude changes are observed for the examined fibers, both can yield an enhancement of amplitude. The paper further investigates the effect of fiber Bragg grating inscription on the overall amplitude of reflected light. The insights gained from this study could be beneficial for controlling the enhancement of light scattering amplitude in fibers with low or high levels of germanium doping. [ABSTRACT FROM AUTHOR]

This paper addresses the challenge posed by the size of certain objects that do not conform to the constraints of microscope‐coupled Raman spectrometers, making sample collection impossible due to their inherent value or nature. Specifically, materials like hydroxyapatite‐based substances used in artistic and ornamental carvings, such as bone or ivory, fall within this problematic category. The focus of this study is the enhancement of analytical capabilities in the context of large objects using a Raman microscope system. The study details the innovation involving a remote probe integrated with fiber optics, elaborating on the design and performance aspects, and emphasizing the appropriateness of chosen components in the analysis of ivory artifacts belonging to private collectors. In order to assess the robustness of our discriminative approaches, an archaeological bone and the exposed dentine in a human tooth were also evaluated and compared. Results showed that using an 805‐nm longpass dichroic mirror successfully directed the near‐infrared laser onto the samples and significantly suppressed the Rayleigh scattering contribution to the spectrum. Regarding the preprocessing methods to spectra evaluation essayed, the most promising approach was the use of principal component analysis for dimension reduction followed by k‐means cluster analysis. By leveraging the complementary strengths of PCA and k‐means clustering, the robustness and interpretability of clustering analyses are enhanced. [ABSTRACT FROM AUTHOR]

Rayleigh scattering from a spherical object located near a planar rigid boundary at distances smaller than the wavelength is calculated. Low frequency analysis reduces a scattering problem to a sequence of potential problems. An analytical solution based on expansion in spherical solid harmonics and the use of addition theorem is presented. Analytical perturbation approach is validated by comparison with numerical calculations. The velocity of the center of the particle and the scattering amplitude are determined. In the lowest order in wavenumber, the scattering amplitude is expressed in terms of the monopole and dipole components. In contrast to the behavior of a bubble, under the same conditions, dipole oscillations of the particle in the direction normal to the boundary are not excited and the monopole component of the scattering amplitude does not depend on the location of the particle relative to the boundary. [ABSTRACT FROM AUTHOR]

This document is an editorial introducing a special issue of the journal Biosensors on the topic of advances in optical biosensors and chemical sensors. The editorial provides an overview of the different types of optical sensors, including fluorescence-based sensors, Raman spectroscopy sensing, and fiber optic-based sensors. It summarizes the main contributions in the special issue, highlighting the working mechanisms and applications of each sensor type. The editorial concludes by discussing the current state of the field and future directions for optical sensor technology. [Extracted from the article]

In order to achieve low-cost scalability, the same-wavelength bidirectional (SWB) fiber communication system is a better solution. We present a detailed investigation of the performance of the different orders Raman amplifiers in same-wavelength bidirectional fiber communication systems. We discuss how to suppress the main factor affecting system performance which is Rayleigh scattering noise (RSN). By using different Raman amplifiers to construct different quasi-lossless transmission, the performance changes in the same-wavelength bidirectional fiber optic communication system were studied. On this basis, multi-channel and same-wavelength single fiber bidirectional system experiments were conducted to compare the performance of second-order Raman systems and first-order Raman systems. The results indicate that the Rayleigh scattering suppression effect of second-order Raman systems is better, and compared to first-order Raman systems, the average signal-to-noise ratio (SNR) can be increased by 2.88 dB. [ABSTRACT FROM AUTHOR]

AbstractNanosurface-imprinted polymer nanoprobes (Fe3O4@MIP) were prepared by microwave synthesis using Fe3O4 as a nanosubstrate, aspirin as a template, α-methacrylic acid (MAA) as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as a cross-linking agent, and 2,2'-azobisisobutyronitrile (AIBN) as an initiator. Characterization of Fe3O4@MIP revealed that the spectral probe exhibited strong resonance Rayleigh scattering (RRS) for aspirin. With the increase in aspirin concentration, the RRS energy transfer (RRS-ET) was enhanced, and the signal at 370 nm decreased, providing a linear range from 0.25 to 12.5 μmol/L and a detection limit (DL) of 0.08 μmol/L. The developed protocol was used for the determination of aspirin in drugs with recoveries from 93.2 to 102.6. [ABSTRACT FROM AUTHOR]

Magnesium aluminate spinel is known to be a material with a good combination of mechanical properties, resistance against chemical attack and a high melting point, being thus a very promising material for application as a transparent material in harsh, high-temperature environments where glass fails. To improve the control over the microstructural evolution during sintering, Eu3+, Y3+ Mg2+ and their combinations were introduced as doping elements. The goal of the study was to optimize processing of fine spinel powder and investigate the potential for enhancing MgAl 2 O 4 spinel density and in-line transmittance by using elements segregating to grain boundaries. The total and in-line transmittance were measured, and the characteristic pore size for transparent samples calculated based on the Rayleigh scattering approximation. Eu-doping proved to be effective in lowering the residual pore size and thus achieving in-line transmittance approaching the theoretical value at relatively low sintering temperatures (1400 °C). [ABSTRACT FROM AUTHOR]